1. Field of the Invention
The present invention relates to a detecting device and a detecting method that detects the state of an internal combustion engine.
2. Description of Related Art
As measures for realizing low fuel consumption in engines (internal combustion engines) and realizing clean exhaust gas, an engine control unit (ECU) is required to correctly detect an engine combustion state to appropriately perform control according to the detected combustion state. As state variables of the engine combustion state, an indicated mean effective pressure (hereinafter referred to as IMEP), a heat release rate (hereinafter referred to as HR), and a mass burn fraction (hereinafter referred to as MBF), and the like are known. For example, there is a technique showing the engine combustion state depending on IMEP (for an example, refer to Japanese Unexamined Patent Application, First Publication No. 2010-261370). According to this Japanese Unexamined Patent Application, First Publication No. 2010-261370, a technique of analytically calculating IMEP is shown, paying attention to a change in cylinder pressure and cylinder volume being periodic. According to this technique, it is shown that IMEP is calculated by operation processing according to an operational expression including, as variables, the amplitude of a fundamental wave included in a cylinder pressure waveform and the amplitude of a secondary harmonic wave, on the basis of the fundamental wave having the rotational frequency of a crankshaft as a fundamental frequency.
Additionally, in recent years, it is expected that vehicles or hybrid cars be equipped with a function to stop an engine at the time of vehicle stop, which realizes low fuel consumption and clean exhaust gas. In the vehicles equipped with the function to stop an engine at the time of vehicle stop, the stop and start of the engine are frequently and repeatedly performed according to the vehicle stop. Additionally, in the hybrid cars, switching between motor drive and engine drive are performed during traveling. When the motor drive and the engine drive are switched during traveling, repetition of the stop and start of the engine is frequently performed. In the vehicles that realize low fuel consumption and clean exhaust gas by the aforementioned switches, the idling state of the engine is reduced and controlled until a stop state is reached, and thus resulting in engine being restarted.
When the engine of a vehicle starts, the operational state of the engine changes greatly similar to a case where acceleration or deceleration of the vehicle is performed. Therefore, when the engine starts or when there is acceleration or deceleration, it is difficult for an engine control unit to appropriately control engine combustion according to the operational state of the engine.